639693640731 has 16 divisors (see below), whose sum is σ = 854344832256. Its totient is φ = 425752614816.

The previous prime is 639693640711. The next prime is 639693640757. The reversal of 639693640731 is 137046396936.

It is not a de Polignac number, because 639693640731 - 2⁶ = 639693640667 is a prime.

It is a super-2 number, since 2×639693640731² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (639693640711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18873706 + ... + 18907568.

It is an arithmetic number, because the mean of its divisors is an integer number (53396552016).

Almost surely, 2^639693640731 is an apocalyptic number.

639693640731 is a deficient number, since it is larger than the sum of its proper divisors (214651191525).

639693640731 is a wasteful number, since it uses less digits than its factorization.

639693640731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44162.

The product of its (nonzero) digits is 13226976, while the sum is 57.

The spelling of 639693640731 in words is "six hundred thirty-nine billion, six hundred ninety-three million, six hundred forty thousand, seven hundred thirty-one".